When it was announced on Tuesday afternoon that Sidney Crosby has been cleared for contact, the next major step in his latest attempt return to the lineup, it sent a wave of excitement and optimism through the Penguins fan base.

It's not hard to see why. He is, after all, their captain, their best player, and the best player in the league when he's healthy. With him in the lineup the Penguins should go from being a Stanley Cup contender to, perhaps, one of the top two or three favorites -- if not the favorite -- in the NHL ... if their lineup remains intact.

His return, whenever it happens (it apparently won't be before Sunday's game against Boston) will certainly have a significant impact on their chances. But, and as crazy as this may sound, there is still another player they are currently without that may be even more important for any sort of Stanley Cup run in Pittsburgh -- defenseman Kris Letang, who is currently out of the lineup after being hit by Eric Nystrom of the Dallas Stars at the end of February.

It's the second time this year he's missed time with a head injury, missing over 20 games with a concussion earlier this season after he was hit by Montreal's Max Pacioretty.

The Penguins have been without Crosby, minus the eight games he played earlier this season, since the beginning of last January, which is over a full calendar year and nearly a season-and-a-half worth of games, and they have still managed to be one of the top teams in the NHL.

In 65 games this season they are the third-highest scoring team in the league (in terms of goals per game) and have the second most points in the Eastern Conference, trailing only the Atlantic Division-leading New York Rangers. It's a testament to the depth they've acquired over the years and the 1-2 punch they still have down the middle at center with Evgeni Malkin (arguably the best player in hockey right now) and Jordan Staal, a duo that few teams in the NHL can match up with.

Even without Crosby they still have another No. 1 center, a darn good No. 2 center, and a pretty potent offense overall. One of the best in the league.

What they don't have without Letang is another No. 1 defenseman, and that's a pretty glaring weakness to have on a potential Stanley Cup team. Their blue line takes on an entirely different look without him, and it simply isn't anywhere near as effective. Just looking at the raw numbers this season: with Letang in the lineup the Penguins are 25-10-5, average over 3.2 goals per game, only allow 2.4 and have a total goal-differential of plus-31.

Without him those numbers drop down to a 14-11-0 record, 2.68 goals for per game, 2.56 against and a total goal differential of just plus-3.

Is Letang by himself worth that entire difference? Well, not exactly, because the Penguins have had other players out of the lineup at various times, but his absence is still huge given the number of roles he's asked to play, and the way he's able to perform within them.

He plays over 25 minutes a night, he is their power play quarterback, a regular on the penalty kill, and during even-strength situations he takes on some of toughest assignments on the Penguins defense, as the scatterplot below, which uses Corsi Relative Quality of Competition and Offensive Zone starts, helps to illustrate. The closer to the top left (meaning tougher opponents and fewer offensive zone starts) the more difficult the assignments, and the closer to the bottom right the "softer" the assignments.

As you can see, the Penguins have a pretty set group of top-four defensemen that stand out from the pack when it comes to their 5-on-5 assignments with Letang, Paul Martin, Brooks Orpik and Zbynek Michalek. Everybody else that's played on their blue line this season has been relatively protected. And when Letang is out of the lineup, as he's been for 25 games and counting this season, one of those other players has to step into a top-four role, and the results aren't always pretty.

Letang not only draws some of the toughest assignments on their blue line, he also outperforms everybody else. He has a positive Relative Corsi rating (a sign that when he's on the ice the Penguins are controlling the puck far more than they are when he's not on the ice) and he is by far their leading scorer on the blue line despite appearing in just 40 games. Orpik is a great physical presence on the blue line, and Martin hasn't been anywhere near as bad as his many critics in Pittsburgh want you to believe that he's been, but none of them are as valuable to the Penguins blue line as Letang.

His ability to get the puck out of danger, lead the rush and control the game is unmatched by any other player on their defense.

Crosby's return will be huge news, and it will give the Penguins pretty obscene depth down the middle. But the return of Letang is what would potentially put the the Penguins over the top, on paper anyway.

I'm still convinced they could win without Crosby due to the presence of Malkin and Staal at center. I'm not convinced they can win without Letang (even with Crosby) because they have nobody else that can fill his skates on defense.

When Sidney Crosby returned to the lineup last month the discussion immediately focussed on whether or not he could win the NHL's scoring title, despite missing the first 20-plus games of the season. As it turns out, Malkin is the Penguins forward we should have been looking at all along.

Thanks to his three-assist performance during a 3-2 win over the Chicago Blackhawks on Tuesday, which came after a five-point destruction of the Buffalo Sabres over the weekend, Malkin moved into a tie for the top spot in the NHL scoring race with 39 points, catching Toronto's Phil Kessel, despite missing six games of his own.

Right now there isn't a more dangerous offensive player in the league, and it couldn't have come at a better time for the Penguins.

For the second year in a row the Pittsburgh roster has been crushed by injuries and on any given night has had some combination of Crosby, Paul Martin, Zbynek Michalek, Jordan Staal and Kris Letang, among many others, sidelined due to various ailments and injuries. Even with all of that, the team has a continued to pile up wins and stay near the top of the conference standings and have the look of a top Stanley Cup contender. Head coach Dan Bylsma certainly deserves a lot of credit for that, as does the Penguins front office, led by general manager Ray Shero, for having the type of organizational depth that allows the team to handle so many injuries to so many key players.

But it also doesn't hurt to have a player like Malkin, one of the most talented and skilled players in the world, that is always capable of taking over a game. And that's exactly what he's been doing for the Penguins this year. For much of this season he's been playing on a line with James Neal and free agent acquisition Steve Sullivan. When the Penguins acquired Neal last season it was done so under the assumption that he would eventually be the goal-scoring winger the Penguins have long been searching for to put alongside Crosby. But with Crosby missing so much time due to injury, Neal has found a home on Malkin's line, and along with Sullivan, have formed a trio that has been Pittsburgh's best on a nightly basis.

"I thought his line in particular, I know Geno is the big guy on that line, but their line played very well in the first," said Bylsma after Tuesday's game. "They attacked in every chance they got over the boards at 5-on-5, and on the power play. They were putting pucks behind and playing in the offensive zone and on the attack."

A couple of years ago Malkin was one of the players consistently mentioned in the "best player in the world" discussion, along with Crosby and Washington's Alex Ovechkin. He won the scoring title during the 2008-09 season and then followed it up with a Conn Smythe performance in the postseason as the Penguins won the Stanley Cup, defeating the Detroit Red Wings in seven games.

But over the past two seasons his production dropped a bit, perhaps due to lingering injuries, and then he missed the last half of the 2010-11 campaign, as well as the playoffs, due to a knee injury that he suffered when Buffalo's Tyler Myers awkwardly fell on his leg during a game last January. Because Malkin has always played second chair in Pittsburgh to Crosby, the face of the franchise, his name has always been the one that's been brought up in absurd trade rumors and baseless speculation for a wide range of reasons (I've brought this up before, but just google "Evgeni Malkin Trade" and start reading), including but not always limited to salary cap concerns, the need to acquire a goal-scoring winger, and, well, pretty much anything that anybody could throw against the wall in the hopes that it would stick. It never did, and for good reason.

Even though Malkin is the "No. 2" center in Pittsburgh (it's probably more of a 1A and 1B deal) when the team is at 100 percent, he has always had a knack for elevating his game when Crosby is out of the lineup. He did it during the 2007-08 season when Crosby missed extended time due to an ankle injury that came after he fell into the boards, and he's doing it again this season. On a per-game average he's actually scoring at a higher rate right now than he was during the '08-09 season when he won his Art Ross Trophy.

"Geno has been a force offensively," said Bylsma on Tuesday. "But he's also a guy we're counting on to play against other teams top lines right now, and he's been good at both ends of the rink. He's been powerful and making plays and driving. He's going to have probably 10 scoring chances again with how he's dominating and how he's playing."

In an effort to improve their overall team defense prior to last season, the Pittsburgh Penguins made two significant investments on their blue line by signing two of the top free agent defenseman that were available on the open market -- Paul Martin, who had spent the previous six years of his career with the New Jersey Devils, and Zbynek Michalek coming off a five-year stint with the Phoenix Coyotes.

Combined, the Penguins committed a total of $45 million over five years to the two rearguards, and the results on the ice spoke for themselves in their first year with the team. The Penguins went from being 20th in the NHL in goals allowed during the 2009-10 season, all the way up to 6th best in 2010-11, while allowing nearly a half-goal fewer per game. That's no small improvement, and the additions of Martin and Michalek were a vital part of it.

Through the first 19 games of this season, Martin has had an up-and-down campaign and seems to be facing a growing amount of criticismfrom the Penguins' fan base for his minus-10 rating entering play on Saturday. That is currently the worst mark on the team and the second-worst mark in the NHL among all defensemen, ahead of only Colorado's Jan Hejda. When you're counting $5 million against the salary cap and near the bottom of the NHL in any category it's going to draw some attention, and hey, every fan-base needs its whipping boy.

So what's wrong with Paul Martin, and is he playing as poorly as the usually misleading plus/minus would suggest?

Nothing that can't be fixed, and not exactly.

So why is his plus/minus currently getting slaughtered? In its simplest terms, plus/minus, in general, and as honestly as it can be said, sucks as a useful measuring stick for the quality of play from a player, and offers little context in to what is going on with the player in question (who is he playing against? What situation is he playing in? Etc.). So let's try and add some context, if we can, and try to better understand his role with two main points that are, in a way, connected to one another.

1) The Penguins aren't scoring goals when Martin is on the ice

And yes, as a player that's on the ice, Martin does have to take some responsibility for this. But it's not going to continue. At least, it shouldn't be expected to continue.

During 5-on-5 play this season the Penguins have scored just four goals with Martin on the ice, which is an extremely low number, especially when you consider the number of minutes he plays. A lack of goals at even strength will obviously have a negative impact on a players rating, and this should not be expected to continue, for this reason: The Penguins, as a team, are shooting just a little over 2 percent when Martin is on the ice during 5-on-5 play, a rate that is unsustainably low over the course of the season.

Of the 536 players that have played a minimum of 10 games this season, only 12 of them have been on the ice for a lower shooting percentage. Look at it another way: If you go back to last season and take the players that played at least half the season in the NHL (40 games), the lowest on-ice shooting percentage belonged to Anaheim's George Parros at 2.54 percent, and he was one of only two players (the other was New Jersey's Adam Mair) that were on the ice for a team shooting percentage of below 3 percent. Over the past four years Martin's teams in Pittsburgh and New Jersey have shot no worse than 7.4 percent over the course of the season with him on the ice.

When you're talking about a player as talented as Martin, playing on a team that scores as often as the Penguins do, eventually, over time, these percentages are going to start work out for Martin, especially when the Penguins generate as many shots on goal as they do with him on the ice.

2) He's playing more minutes than any other player on the team, and he's being asked to play some of the "toughest" minutes on the team

Due to various injuries, including Michalek and Brooks Orpik, as well as a two-game suspension to Kris Letang, Martin has played significantly more minutes than any other player on the team. Entering Saturday he's at 464 overall minutes, 351 of which have come during even-strength play. Letang is the only other player on the team to crack the 300-minute mark at even-strength, while no other player is over 285. Not only is he playing more often than everybody else, he's playing in significantly more difficult situations.

You can tell a lot about a player, and what that player's coach thinks of him, by the situations he's put into. This season Dan Bylsma and his staff are giving Martin some of the tougher assignments in the NHL, and definitely the toughest assignments on the team. Consider his QualComp (Quality of Competition -- the higher the number, the tougher the competition) numbers and the limited number of Offensive Zone face-offs he's been on the ice for.

The only Penguins defensemen that's seen tougher competition is Orpik, while no other defensemen has started fewer shifts in the offensive zone.

Martin's game has definitely hit a bit of a rough patch over the past couple of weeks, and he's had his moments where he's been beat by opposing players one-on-one. But there's also a lot of things working against him right now, including some bad luck (hello, unsustainably low shooting percentage) and playing some of the heaviest minutes on the team, and playing a lot of them.

That's an extremely difficult role. Playing against the other team's best players and starting most of your shifts in your own zone (defensive zone faceoffs are dangerous) is a difficult task for any player, and will have an impact on your ability to score, as well as the other team's ability to score against you. Players that play the most minutes against the best players in the toughest spots will see the more goals scored against them and have a more difficult time scoring goals.

Take another look at the above table and look at the quality of players Matt Niskanen, for example, plays against, and the number of shifts he gets to start in the offensive zone. He's a team-best plus-five this season. No disrespect to Niskanen intended, but there isn't a coach or GM in the NHL that would take him over Martin, now, or at any other point. Give Martin those minutes and assignments, and vice versa, and see what their ratings look like.

I went back and looked at every goal that's been scored against the Penguins this season that would count against his plus/minus, and there's some pretty fascinating things in there. On at least two of them the Penguins were stopped on prime scoring chances at the other end of the ice before the play went back the other way and resulted in a goal at the other end. On one of them his defensive partner, Michalek, fell down on the opening face-off in Winnipeg which resulted in a flukey turnover -- and goal -- eight seconds into regulation.

None of this is likely to change the opinion of the person that takes his plus/minus rating as gospel, but if you think he's currently the second-worst defenseman in the NHL, or somehow not worth the cap hit to the Penguins, you're simply wrong.

The Penguins defense is a critical part of their success, and Martin is, and will continue to be, a key cog in that machine.

Sooner or later all of these injuries for the Penguins have to stop, right? Head coach Dan Bylsma announced on Monday that defenseman Zbynek Michalek will be sidelined between four-to-six weeks due to a broken finger that he suffered while blocking a shot during their 4-1 win over the New Jersey Devils on Saturday night.

Michalek signed a five-year, $20 million contract with the Penguins prior to last season and has been a steady presence on their blue line ever since. He's been one of the best shot-blockers in the NHL throughout his career, and along with the addition of Paul Martin, was a big factor in helping the Penguins reduce their goals against average by nearly half a goal per game during the 2010-11 season.

His injury is simply the latest one for a Penguins team that's been dealing with them all season, and it comes just two games after Brooks Orpik, perhaps their best defensive-defenseman, made his season debut last week. Orpik missed the first eight games of the season while he recovered from offseason surgery. The Penguins have also been playing without their captain and best player, Sidney Crosby, as he attempts to return from his concussion, while Evgeni Malkin, their second best player, and Tyler Kennedy have also missed significant time this season with injuries. Kennedy is out indefinitely with a concussion, while Malkin is still day-to-day.

With Michalek sidelined that likely means Ben Lovejoy will have an opportunity to return to the lineup, as he was the odd man out once Orpik made his debut and Kris Letang returned from his recent two-game suspension.

The incredible run of injuries that arguably helped derail the Pittsburgh Penguins season a year ago has found a way to continue during the start of the 2011-12 season. Playing without Sidney Crosby, Evgeni Malkin, Brooks Orpik, Tyler Kennedy and Kris Letang (though, his recent absence was the result of a suspension) at various times, a group of players that adds up to nearly half of their salary cap commitments for the year, they have still managed to win five of their first nine games and earn at least a point in seven of them.

They've done all of this while being outscored during 5-on-5 play (18-14), and with a power play that has slumped down to a 10 percent rate over the past seven games, scoring on just three of its past 29 attempts. One of the most important aspects of their fast start has been a penalty killing unit that has been as dominant as any other group in the league. This isn't exactly a new development for the Penguins, as they finished with the top spot in the NHL last season at just over 86 percent. Through the first nine games this season they look to be even stronger.

Pittsburgh has found itself in a shorthanded situation 31 times this season and has only allowed one goal to the oppositions power play. That goal came during a 4-on-3 power play, typically considered a tougher penalty to kill than a traditional 5-on-4 due to the extra space the power play has to work with, in overtime during their loss to the Washington Capitals last Thursday.

Other than that? They've been perfect. Even more impressive is the fact the Penguins have already managed to score three shorthanded goals this season. They're not just stopping the other team's power play from scoring, they're flat out beating them on the scoreboard. At this point there is only one other team in the NHL on the "plus" side of the scoring while shorthanded, and that's Chicago which has a 2-1 edge during its 17 shorthanded situations.

When talking to opposing players after some of their recent games the one common theme everybody keeps bringing up is how aggressive the Penguins are on the penalty kill. And that's not really anything new. Every team says it wants to be aggressive, or take away time and space, or whatever other coaching cliche you can throw out there. But the Penguins seem to take it even further than most teams and never let up. Panthers defenseman Brian Campbell called them "relentless" following a performance that saw his team go 0-for-4 on the man advantage and surrender a shorthanded goal during a 4-2 loss last Tuesday.

Such an aggressive style while down a man has a potentially large payoff -- like, say, a shorthanded goal -- but also carries some risk if you're not wisely picking and choosing your spots, which is something Canadiens defenseman P.K. Subban brought up following Thursday's game -- they don't put themselves in bad situations.

"They pressure the right way and they pressure at the right times," Said Subban. "They play a smart game. They don't put themselves in trouble, they play smart, they limit your opportunities and they have guys that are willing to sacrifice."

Goaltenders generally get the most attention for a team's strong penalty kill, and Marc-Andre Fleury and Brent Johnson have both been excellent in shorthanded situations this season. But Pittsburgh also does a fantastic job of not allowing teams to even get an opportunity to create shots or establish any sort of presence in the offensive zone. Through nine games the Penguins are allowing just .768 shots per minute in shorthanded situations, a mark that is eighth-best in the NHL and well below the league average (at this point) of .857.

They're willing shot-blockers and do an excellent job of not allowing teams to gain a clean entry into the zone or get an opportunity to set up their power play, and that's a testament to the play of forwards like Jordan Staal, Craig Adams, Pascal Dupuis and Matt Cooke, as well as defenseman Paul Martin and Zbynek Michalek. More than one Canadiens forward, including Brian Gionta, commented on Thursday night about his team's struggles to generate any speed through the middle of the ice

"I haven't seen many of their other games," said Gionta. "But tonight we had a hard time getting up through the neutral zone, and when you don't come clean through there and you're trying to win battles to get the puck back it's basically 50-50."

With players like Crosby and Malkin out of the lineup the Penguins aren't going to put up the type of offensive numbers typically seen from them, and they're going to have to keep grinding out wins. Completely shutting down the other team's power play is a good place to start.

Set to become an unrestricted free agent following this season, it was announced on Thursday morning that Chris Kunitz has signed a two-year contract extension with the Pittsburgh Penguins. The deal is worth $3.275 million per season according to the team, which is a salary cap hit that is identical to the that came with his previous contract.

Since being acquired by the Penguins, along with Eric Tangradi, from Anaheim in 2009 in exchange for defenseman Ryan Whitney, Kunitz has scored 43 goals in 140 regular season games, typically playing on a line with Sidney Crosby when both have been in the lineup.

He's not the flashiest player on the Penguins roster, but over an 82-game season he maintains a 50-60 point pace and seems to play the type of physical, aggressive game head coach Dan Bylsma likes, while also having a willingness to go to the front of the net and do the dirty work around the crease. He's been a good fit within their system. The only downside to his play the past couple of years is that he's had to miss 48 games due to injury over the past two seasons.

With Kunitz now in the mix for the next two years the Penguins have just about every core player on the roster signed signed through at least next season, including Crosby, Evgeni Malkin, Jordan Staal, Kris Letang, Paul Martin, Zbynek Michalek and Marc-Andre Fleury. Many of them are signed for at least the next two years, with the exception of Crosby and Staal, who would be eligible for unrestricted free agency following next season.

As it stands now, the Penguins have roughly $54 million in salary cap committments to 17 players for the 2012-13 season, via Capgeek, which would leave them with somewhere in the neighborhood of $10 million in cap space (assuming there are no changes to the cap).